active sub filter questions

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I'm looking at this subwoofer filter kit:

http://www.altronics.com.au/index.asp?area=item&id=K5562

An externally hosted image should be here but it was not working when we last tested it.


I have a similar kit already in my system, however this one has an "auto power on" function, which I was going to add to my system at greater cost than this kit, for a mains slave switch kit.

* can anyone advise on modifying this kit (given a schematic) to lower the xo point (only goes as low as 60 Hz, and I'd like to have it xo at 40 Hz)?

* how does one use it to get a separate power amp to power up? Will this work for switching on any separate amp?

Previously I was going to get one of these kits:

http://www.altronics.com.au/index.asp?area=item&id=K6046

An externally hosted image should be here but it was not working when we last tested it.


but it seems like the sub processor kit will do a similar job. Am I right? I understand how the mains slave trigger kit works, but not sure about auto power on ...
 
paulspencer said:
JDeV,

I currently have a similar kit which is available at Jaycar www.jaycar.com.au which is in Australia

It has a variable LP filter, a defeatable 20 Hz 3rd order rumble filter, and one band of parametric eq.

For the moment I'm happy with it. Easy to build and has the basics. Soon I'll be trying out DCX as a 3way active xo.

Paul
Are you talking about the Behringer DCX2310?
I'm thinking about using it.
What driver are you using btw?
 
David,

You must mean Behringer Ultradrive - DCX 2496 - 3 way digital active xo, right?

With your speakers you might even consider Clarity Eq - more expensive but its more powerful and also has eq, and you can buy a refurbished unit for $1500ish IIRC. It has features similar to Ultradrive and Ultracurve which together at a good price well below retail go for about $1000.

DCX I'd expect to be able to get hold of for about $390, based on discount off retail I got last year. I'm looking at doing a group buy this Christmas, since as a group we can more likely get a good price. If we can get price down to $350 as a group that would be nice! There is a group buy for the US, but we really need to buy from here to get reliability, the service centre guy told me units bought overseas are notoriously unreliable here due to the power supply, even though they can be switched.

Shoot me an email if you like
 
paulspencer said:
JDeV,

I currently have a similar kit which is available at Jaycar www.jaycar.com.au which is in Australia

It has a variable LP filter, a defeatable 20 Hz 3rd order rumble filter, and one band of parametric eq.

Hi Paul,
Do you maybe have a circuit for this that I may have a look at?
I build one myself a while ago, but does not work very well anymore.

Controller
 
David,

I bought my subs from Stryke (now AE speakers). I purchased during pre-order so they were only $120 each USD, but after adding 5% customs and shipping, they cost $320 each, which I was happy with at the time since a Shiva would have cost only $20 less and I find this a lot more impressive than a Shiva! 23mm xmax, very nicely built, high power handling, and a stylish aluminium cone.

JD,
Here is a schematic:
 

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JDeV,

I've seen the ESP project.
I opted to go with something similar, but it was in kit form. I find kits usually offer the best value for money, and you often pick them up for less than the cost of the parts. The kit is available at Jaycar or Altronics in Australia. I followed the instructions meticulously and it worked fine without issue. You may have some issues with operating in a country with a different voltage - here we have 240V and you would have to be careful of course that mains wiring is correct.

Have you tried posting on the ESP forum?

It would be a shame to go to the effort and cost of sourcing components, then leave it and start again. I know my kit took a long time to build, especially since I modified mine. I added key switch which needed a 12V power supply to operate the relay so that it could be used for mains switching. Since all my audio stuff is hooked up to this unit, I can disable it all with a key! I only use the key when I've made some kind of change in my system to make it unsafe to use.
 
paulspencer said:
David,

You must mean Behringer Ultradrive - DCX 2496 - 3 way digital active xo, right?

With your speakers you might even consider Clarity Eq - more expensive but its more powerful and also has eq, and you can buy a refurbished unit for $1500ish IIRC. It has features similar to Ultradrive and Ultracurve which together at a good price well below retail go for about $1000.

DCX I'd expect to be able to get hold of for about $390, based on discount off retail I got last year. I'm looking at doing a group buy this Christmas, since as a group we can more likely get a good price. If we can get price down to $350 as a group that would be nice! There is a group buy for the US, but we really need to buy from here to get reliability, the service centre guy told me units bought overseas are notoriously unreliable here due to the power supply, even though they can be switched.

Shoot me an email if you like

Thanks Paul.
Actually I'm after an analog EQ purely for subwoofer duties (digital would be overkill). I may end up using the Elliot design.
 
David, you can buy this kind of thing so cheap I wouldn't even consider diy in this case. You could probably pick up Feedback destroyer for as low as $150 new:

http://www.behringer.com/DSP1124P/index.cfm?lang=ENG

An externally hosted image should be here but it was not working when we last tested it.


It has 24 bands of fully parametric eq. A diy will likely cost you more if you get any kind of decent case.

What sub are you using or considering?
 
Hi Paul
Currently I'm considering 2x10" Peerless XXLS in either the one 70litre cabinet or in 2 separate 35 litre enclosures (to allow for more placement options). All I want & need is a 2nd order lowpass at 40Hz (adjustable) to drive the sub(s), which seems perfect for a simple op-amp design. Problem is, it's hard to find such an item except in kits, so I'll probably take that path. Powering it is a concern though. If I power on the amp before the filter the consequences could be catastrophic!
I'm not convinced about a digital processor. Also wouldn't it introduce a time delay?

edit... actually, now that I think about it, a passive line-level 2nd order may be the best & safest option.
 
David,

I tend to prefer the flexibility of separate smaller enclosures. This allows one option in particular which is quite interesting - putting them far apart and reversing polarity on one of them so they act as a dipole with a very low fequal, reducing room interaction, also keeping more bass in the room.

Jaycar have a kit that will do this. It also has a single band of parametric eq. This is what I use. It's a kit for only about $30. The simplest and cheapest way to power one of these is with a plugpack, one which you may have lying around from a pair of computer speakers, unused printer, etc.

If I power on the amp before the filter the consequences could be catastrophic!

how? ... are you talking about thumps?

One of the simplest ways to handle this is to turn it all on and off via the power point. I get less hassles this way, as some components have a noisy turn on/off due to arking of the switch, which is much less likely to happen on a GPO wall outlet. I actually use a power up kit which automatically switches on all my audio stuff when it senses power going to the DVD player. Hence it all goes on/off with remote!

I used to go through that painful routine of turning on each thing in a particular routine ... even turning up and down passive attentuators. It was like some bizarre religious ritual! Now I just sit in my seat and press a button on the remote! ;)

A digital unit will introduce a tiny delay which is equivalent to the sub being placed about a foot back. You won't notice the difference. I have experimented with digital delay and it gets to be much more than this before you can notice it!

The problem with a fixed crossover is that you may set the fc @ 40 Hz, but the actual resulting -3db points will vary considerably to what you had in mind. You might need to set the fc @ 30 Hz to actually get a -3db point @ 40 Hz, this is why you want a variable LP filter, otherwise it's a case of playing darts blindfolded and hoping to hit bullseye!
 
Thanks Paul
Yes, thumps are my concern, and l really don't want to have to deal with a turn-on routine.
At this stage I'm working on a passive line-level 2nd-order filter which has a simplicity that is very appealing .
The crossover will be semi-fixed - I'll make some sort of plug/socket arrangement to allow easy changing of resistors /caps to get the right fc from say 30,40, 50 Hz.

What's your opinion of the Peerless XLS range in comparison to the Stryke? I'm about to take the plunge.
 
David,

The XLS and the AV12 are two very different drivers. The XLS will go smaller in a PR/vented alignment, although if you are going sealed then that's irrelevant.

The AV12 has twice the displacement - 2.3L vs 1.1L which means a sealed AV12 can match the XLS in a PR box in terms of SPL.

It has a larger SD and twice the xmax.

It also has a much higher power handling, more than double the XLS.

I think the advantage with the XLS is distortion. I don't have measurements to back this up, but I think its top end is a bit more articulate. If you want to cross high, up around 80 Hz then this is an issue. If you cross low, around 40 Hz then its less of an issue, although something which has caught my attention lately is that a subwoofer will have harmonic distortion content above its passband. A 40 Hz tone will produce 2nd order harmonics at 80 Hz, and 3rd order at 120. With this in mind, you want to be careful that the sub you get won't mess up the low distortion performance of your mains. I think the XLS is likely a better choice for you, although the TC2+ is slightly better and there are quite a lot of new subs around now which would also be a bit better.
 
Thanks Paul.
I've ordered the Peerless!
As I'm using 2nd order at about 40Hz, distortion and bandwidth are somewhat relevant, as is a compact size, and at the price they are hard to beat IMO.
I agree with what you said about distributing subwoofers around the room. At this stage I plan to have them as stands for my surround speakers to minimise impact on floor space.
With the mains included, I'll then have 4 x 10" woofers providing my bottom end. Should rock the house ;)
BTW how are those curved subs coming along?
 
Well, after my calulations showed that a 2nd order passive lin-level was too much of a load for the pre-amp, I decided to purchase this Pyramid car active filter, which I'll be using to drive my subwoofer only:

Pyramid CR73G 6 Channel Electronic Crossover System
Compact Half DIN Size
Mounts in or under Dash
6 Channel RCA Output (Sub, Mid, High)
2 Channel RCA Input Jacks
Infinitely Adjustable Crossover Points
Sub:32-400Hz
Mid:32-400Hz
High:640-8000Hz
Independent Output Gain Control per Band (3)
Subwoofer Phase Shift Adjustment
Frequency Extender (Factor 1:20)
LED Power On Indicator
Fully Isolated DC to DC Power Supply
12dB per Octave Slope
Frequency Response:20Hz-30kHz
Signal to Noise Ratio:>90dB
Distortion:0.01%@1kHz
Dimensions: 7” W x 1” H x 5” D

Cost US$35
 

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